Is there anything *good* that sits in between the two extremes of SQLite 
and PostgreSQL?

I've tinkered with MySQL years ago (in conjunction with PHP) and was a 
little unhappy with some of the things it either didn't implement fully 
(foreign keys) or silently ignored (check constraints).  PostgreSQL, to 
me, is orders of magnitude harder to set up and maintain, though.  And 
then there is SQLite, which does 99% of what I want it to do other than 
network use.  I see other DB names such as DB2, Oracle, MS SQL Server, 
etc. out there but the only other 'free' one seems to be Firebird?  Is 
that really the only other contender?  Is there nothing that amounts to 
a 'PostgreSQLite'?

http://article.gmane.org/gmane.comp.python.general/772126/match=firebird